The broad objectives of this project are to understand the processes of visual detection, recognition, and perception in humans and to understand how visual information is dealt with in the brain. The experimental techniques will be the performance of visual psychophysical experiments on human subjects. One method will involve signal to noise considerations and quantum efficiency in visual detection. The other approach will be through the study of rod monochromacy, afterimages, adaptation and rod saturation. The latter method will be used both to study underlying mechanisms as well as to study techniques for improved diagnosis of monochromacy and the use of weak afterimages as a method of reducing their photophobia.